| Ultimate tensile strength |
The greatest tensile strength that a material can withstand. |
| Ultrasonic |
Vibrations generated at frequencies above the range of human hearing capabilities. |
| Ultrasonic inspection |
A nondestructive testing method in which ultrasonic waves are passed through the material being inspected.Echo patterns will locate any discontinuities. |
| Ultrasonic transducer |
A device used to generate ultrasonic vibrations that, in turn, vibrate the sonotrode to perform ultrasonic welds. |
| Ultrasonic welding |
A process used to weld metal or other material through use of ultrasonic vibrations. |
| Ultraviolet rays |
Energy waves that emanate from the welding arc.These waves are of such a frequency that they are in the ultraviolet ray light spectrum. |
| Undercut |
A depression at the toe of the weld which is below the surface of the base metal. |
| Undercutting |
The thinning of the base metal along the toe of the weld. |
| Underfill |
A depression on the face of weld or root surface extending below the surface of the adjacent base metal. |
| Under load |
In arc welding, the term is used to describe the state of the welding machine when current is flowing through the welding circuit (while welding or with the electrode holder touching the table or workpiece). |
| Unstable arc |
An arc that has not established itself in the ionized space between the electrode and the workpiece.An unstable arc may wander or stop. |
| Upset |
The term used to describe the enlarged weld where the parts meet in a friction weld. |
| Upslope |
The rising line on a current/time program graph. |
